During the 1972 Olympics, the swimmer Mark Spitz won seven gold medals and set several World records. Horst Dassler saw this as an opportunity to get into the swimwear business but Adi would not do it. Instead of starting swimwear with Adidas Horst decided to start a separate company that would make swimwear. Horst called this new company Arena and signed a deal with Spitz when he retired after the 1972 Olympics. Horst Dassler grew this new business and at the World Championships in Cali, Columbia, about two thirds of the swimmers wore Arena. I think it is very cool that Horst Dassler started this business separately from Adidas and was able to grow it so fast.
The Dassler Brothers